Recording medium controller and method thereof

ABSTRACT

According to one embodiment, a recording medium controller includes a recording medium, an input module, a reading module, and a writing module. The recording medium includes a write area and an escape area. The write area includes track groups. Each of the track groups is a unit for writing data and includes tracks. The input module receives a write command for data. The reading module reads data stored in the escape area and data from a first track group of the track groups. The writing module writes data received for the write command to the escape area, and writes merged data obtained by merging the data read from the escape area and the data read from the first track group to each track of a second track group of the track groups by using a shingle recording technique in which adjacent tracks are partly overlapped with each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-124898, filed May 31, 2010, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a recording mediumcontroller configured to write data to a recording medium using theshingle recording technique, and to a method thereof.

BACKGROUND

A hard disk drive (HDD) comprising a magnetic disk has conventionallybeen used. The recent trend is to further increase the capacity of ahard disk. In order to increase the recording density for increasing thecapacity, there has been disclosed a technique in which the trackdensity is decreased by reducing track widths.

There has also been disclosed another technique for increasing the trackdensity. In this technique, the track widths are decreased to an extentthat data is written to adjacent tracks in a partly overlapping manner.Such a recording technique is often referred to as shingle recording.However, when this technique is applied, the data stored in the adjacenttrack in a partly overlapping manner is lost. Therefore, data writingmust be performed per unit track group composed of a plurality of tracks(for example, see Japanese Patent Application Publication (KOKAI) No.2006-338731).

However, employing the technique disclosed in Japanese PatentApplication Publication (KOKAI) No. 2006-338731 takes long time to writedata because the writing must be performed per unit track group.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various features of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention.

FIG. 1 is an exemplary perspective view of a magnetic disk deviceaccording to an embodiment;

FIG. 2 is an exemplary block diagram of an electrical hardwareconfiguration of the magnetic disk device in the embodiment;

FIG. 3 is an exemplary block diagram of a software configurationrealized by a central processing unit (CPU) of the magnetic disk deviceexecuting a computer program, in the embodiment;

FIG. 4 is an exemplary schematic diagram of recording areas on amagnetic disk to which data is written by a writing module in theembodiment;

FIG. 5 is an exemplary schematic diagram illustrating a process ofwriting data to an escape area by the writing module when an inputmodule receives a command for updating data, in the embodiment;

FIG. 6 is an exemplary schematic diagram illustrating a process in themagnetic disk drive, and in which data stored in the escape area iswritten to a track group comprised in a write area, in the embodiment;

FIG. 7 is an exemplary flowchart of a writing process of the magneticdisk device performed in response to a write command, in the embodiment;and

FIG. 8 is an exemplary flowchart of a process of the magnetic diskdevice, and in which data stored in the escape area is written to thetrack group, in the embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a recording medium controllercomprises a recording medium, an input module, a reading module, and awriting module. The recording medium comprises a write area and anescape area temporarily storing data therein. The write area comprisestrack groups. Each of the track groups is a unit for writing data andcomprises a plurality of tracks. The input module is configured toreceive a write command for data. The reading module is configured toread data stored in the escape area and data from a first track group ofthe track groups. The writing module is configured to write datareceived for the write command to the escape area, and to write mergeddata obtained by merging the data read from the escape area and the dataread from the first track group to each track comprised in a secondtrack group of the track groups by using a shingle recording techniquein which adjacent tracks are partly overlapped with each other.

An exemplary embodiment of a magnetic disk device using a recordingmedium controller and a recording medium controlling method is describedbelow in greater detail with reference to the drawings. However, theembodiment described hereunder is not intended to limit the scope of thepresent invention in any way.

A mechanical structure of the magnetic disk device according to theembodiment will now be explained with reference to FIG. 1. FIG. 1 is aperspective view of the magnetic disk device according to theembodiment.

A magnetic disk device 1 illustrated in FIG. 1 comprises a magnetic disk11, a spindle motor 12 configured to rotate the magnetic disk 11, a headslider 13 in which a magnetic head (not illustrated in FIG. 1) isincorporated, a suspension 14, and an actuator arm 15 in a housing 10 asmain mechanical components thereof in the same manner as in a known harddisk drive. The magnetic disk device 1 also comprises a head suspensionassembly configured to support the head slider 13, and a voice coilmotor (VCM) 16 that is an actuator for the head suspension assembly.

The spindle motor 12 rotates the magnetic disk 11. A magnetic headhaving a recording head and a reproducing head (neither of which isillustrated in FIG. 1) is incorporated in the head slider 13. Theactuator arm 15 is mounted on a pivot 17 in a rotational manner, and thesuspension 14 is attached to one end of the actuator arm 15. Thesuspension 14 supports the head slider 13 flexibly via a gimbal disposedthereon. The VCM 16 is located at the other end of the actuator arm 15.The VCM 16 rotates the actuator arm 15 about the pivot 17 to bring thefloating magnetic head at a certain position in the radius direction ofthe magnetic disk 11.

An electrical hardware configuration of the magnetic disk device 1according to the embodiment will now be explained with reference to FIG.2. FIG. 2 is a block diagram of the electrical hardware configuration ofthe magnetic disk device 1 according to the embodiment.

In FIG. 2, the spindle motor 12 (FIG. 1) rotates the magnetic disk 11about a rotation axis at a predetermined rotation speed. A motor driver21 drives rotation of the spindle motor 12.

A magnetic head 22 uses the recording head and the reproducing headcomprised therein to read and to write data from and to the magneticdisk 11. As mentioned earlier, the magnetic head 22 is placed at thedistal end of the actuator arm 15, and moved in the radius direction onthe magnetic disk 11 by the VCM 16 driven by the motor driver 21. Whenthe magnetic disk 11 is not under the rotation, for example, themagnetic head 22 is evacuated onto a ramp 23.

A head amplifier 24 amplifies a signal read using the magnetic head 22from the magnetic disk 11, and outputs the signal to a read/writechannel (RDC) 25. The head amplifier 24 also amplifies a signal receivedfrom the RDC 25 for writing data to the magnetic disk 11, and suppliesthe signal to the magnetic head 22.

The RDC 25 performs a code modulation on data received from a HDC 31 tobe explained later and to be written to the magnetic disk 11, andsupplies the data to the head amplifier 24. The RDC 25 also performs acode demodulation on a signal read from the magnetic disk 11 andreceived via the head amplifier 29, and outputs the signal to the HDC 31as digital data.

A central processing unit (CPU) 26 is connected to a static randomaccess memory (SRAM) 27 that is a working memory, a flash read-onlymemory (ROM) 28 that is a non-volatile memory, and a buffer randomaccess memory (RAM) 29 used as a temporary memory. The CPU 26 controlsthe entire magnetic disk device 1 in accordance with firmware pre-storedin the flash ROM 28 and the magnetic disk 11. (This firmware comprisesinitial firmware and controlling firmware used for regular operations.The controlling firmware further comprises a magnetic disk controllingprogram, which is to be explained later. The initial firmware, which isexecuted initially upon booting, is stored in the flash ROM 28. Thecontrolling firmware, which is used for regular operations, is stored inthe magnetic disk 11. The controlling firmware is read once from themagnetic disk 11 to the buffer RAM 29 following a control performed bythe initial firmware, and then stored in the SRAM 27.

The hard disk controller (HDC) 31 controls data transmissions andreceptions performed between the magnetic disk device 1 and a hostcomputer (hereinafter, simply referred to as “host”) 40 via an interface(I/F) bus, controls the buffer RAM 29, and performs error corrections ondata. The buffer RAM 29 is used as a cache for data transmitted to andreceived from the host computer 40. The buffer RAM 29 is also used fortemporarily storing therein data read from or to be written to themagnetic disk 11, and the controlling firmware read from the magneticdisk 11, for example.

FIG. 3 is a block diagram of a software configuration realized by theCPU 26 comprised in the magnetic disk device 1. Here, the CPU 26executes the magnetic disk controlling program to realize the softwareconfiguration. As illustrated in FIG. 3, the CPU 26 comprised in themagnetic disk device 1 starts the magnetic disk controlling programcomprised in the controlling firmware stored in the flash ROM 28 torealize an input module 301, a writing module 302, a reading module 303,and a merging module 304.

The input module 301 receives data write commands or data read commandsfrom the host 40 connected to the magnetic disk device 1. Examples ofthe data write commands comprise a write command for data having a sizestorable in a sector comprised in a single track of the magnetic disk11, or sequential write commands for data having a larger size.

The writing module 302 controls writing data to the magnetic disk 11.When the writing module 302 according to the embodiment performs writecontrols, the writing module 302 needs to write data to a track having awidth smaller than the main pole width of the magnetic head 22.

Therefore, the writing module 302 according to the embodiment performswrites using the shingle recording technique. The shingle recordingtechnique is a technique for writing data in an overlapping manner whilescanning an extremely small amount along the track direction by therecording head. Because the track width of the magnetic disk 11 used inthe shingle recording technique is smaller than the main pole width ofthe recording head, data written to adjacent tracks partly overlap eachother. Because the smaller track width can be used when the shinglerecording technique is adopted, the density of a medium can beincreased.

In the shingle recording technique, data in adjacent tracks is lostbecause the data in adjacent tracks are written in partly overlappingmanner. Therefore, even when particular data in a certain track is to beupdated, the particular data alone cannot be updated, but whole data ina number of tracks needs to be updated. In this embodiment, such unit oftracks is referred to as a track group. Here, an unused area is providedbetween the track groups. Thus, when data is written to one of the trackgroups, data in other one of the track groups adjacent the one of thetrack groups is protected from being overwritten.

FIG. 4 is a schematic diagram of a recording area on the magnetic disk11 to which data is written by the writing module 302. As illustrated inFIG. 4, the magnetic disk 11 comprises a write area 402 used as aregular data recording area and an escape area 401 used as temporarystorage area for the data.

The write area 402 comprises a plurality of track groups (a track group403, for example). As mentioned earlier, each of the track groupscomprises a plurality of tracks, each having a width smaller than themain pole width of the head performing the writes. The number of trackscomprised in the track groups is not limited, but the number of tracksin the following explanation is assumed to be 100.

The write area 402 comprises not only track groups assigned with logicaladdresses, but also those not assigned with logical addresses. In theembodiment, a track group not assigned with a logical address isreferred to as a spare track group. The number of spare track groupsallocated in the write area 402 is not limited, and a plurality of thespare track groups may be allocated. In the magnetic disk 11 accordingto the embodiment, the tracks comprised in the magnetic disk 11 areconcentrically divided by head/zone. A number of sectors per track aredifferent for the head/zone. More specifically, the number of sectorsper track is larger in one of the heads/zones located nearer to theouter circumference. In other words, the capacity of the tracks isdifferent for the heads/zones. Thus, in the magnetic disk 11 accordingto the embodiment, a spare track group is provided for each head/zone.In this manner, because a spare track is provided for each of theheads/zones, the entire data written in a single track can be written toa single spare track, even if the capacity of the tracks is differentfor each of the heads/zones.

The escape area 401 temporarily stores therein data to be written to thewrite area 402. Assuming that a single platter of the magnetic disk 11has a capacity ranging from 500 gigabytes to one terabytes, the escapearea 401 of several gigabytes is provided, for example.

The reason why the escape area 401 is comprised in the magnetic disk 11will now be explained. To rewrite data using the shingle recordingtechnique, the data in the entire track group needs to be rewritten.Therefore, much longer time is required than a conventional datarewriting technique. Thus, in the magnetic disk device 1 according tothe embodiment, the temporary escape area 401 is provided. Then, at thetime when the writing module 302 writes data in accordance with a writecommand, the data is temporarily written to the escape area 401 insteadof the track group in the write area 402. In this manner, the timerequired for the writing is reduced.

The escape area 401 according to the embodiment is located on the outerside of the magnetic disk 11. In this manner, the writing and thereading speeds can be improved.

The escape area 401 may be a group of tracks each with a small trackwidth so that data is written using the shingle recording technique.Alternatively, the escape area 401 may be a group of tracks each with aconventional track width so that data can be written without data ofadjacent tracks being overlapped.

The reading module 303 reads at least one of the data stored in theescape area 401 and the data stored in the write area 402 when the inputmodule 301 receives a read command or when the data written in themagnetic disk 11 is to be updated.

FIG. 5 is a schematic diagram illustrating a process of writing data tothe escape area 401 performed by the writing module 302 when the inputmodule 301 receives a command for updating data. In the exampleillustrated in FIG. 5, it is assumed that the input module 301 receivesa write command for data to be written to a sector 503 in a track 2comprised in a track group 501. If the data at the sector 503 is updatedusing the shingle recording method, the entire track group 501 must beupdated. This process will require long time.

Therefore, in the embodiment, when the input module 301 receives anupdate command for a part of a track or a sector (e.g., the sector 503)of a track group to which data from the host 40 is already stored, thewriting module 302 writes data corresponding to the update command to atrack or a sector (e.g., sector 504) of the escape area 401.

After the writing, the writing module 302 reassigns a logical addressthat has previously been assigned to the track or the sector to beupdated (e.g., the sector 503) to the track or the sector in the escapearea 401 (e.g., sector 504). This process ends the writing performed forthe update command received by the input module 301.

When such process is performed continuously, the capacity of the escapearea 401 will be overused. Thus, to avoid overusing the capacity of theescape area 401, in the magnetic disk device 1 according to theembodiment, the data stored in the escape area 401 is written to thewrite area 402. This writing process is performed during an idle timeexcluding a time during which the input module 301 is performingprocesses in response to the read or write commands.

In the writing process performed during the idle time, the data storedin the escape area 401 and the data stored in the track group that isbeing updated are merged. In other words, in the magnetic disk device 1according to the embodiment, because the merging is performed during theidle time, the merging does not interrupt executions of processesperformed for read or write commands issued by the host 40, and theexecutions of such processes are not delayed.

During the idle time, the merging module 304 merges the data read fromthe escape area 401 and the data read from the track group in the writearea 402, each of which is read by the reading module 303, by using abuffer (not illustrated).

The writing module 302 then writes the data merged by the merging module304 to each of the tracks comprised in a spare track group, which isarranged separately from the track group read by the reading module 303.

FIG. 6 is a schematic diagram illustrating a process of writing the datastored in the escape area 401 to the track group in the write area 402,performed by the magnetic disk device 1 according to the embodiment.FIG. 6 illustrates an example where the merging module 304 merges thedata stored in the sector 504 in the escape area 401 by the process ofFIG. 5 and the data stored in the track group 501, and where the writingmodule 302 writes the merged data to the spare track group.

As illustrated in FIG. 6, the writing module 302 writes the data read bythe reading module 303 from the track group 501 to a spare track group601. During this process, the reading module 303 also reads the datafrom the sector 504 comprised in the escape area 401. The merging module304 then merges the data read from the sector 504 comprised in theescape area 401 and the data read by the reading module 303 from a track2 comprised in the track group 501. The writing module 302 then writesthe merged data to the spare track group 601.

After completing writing the data of the track group, the writing module302 reassigns the logical address assigned to the track group 501 whichis the target of the updating to the spare track group 601, and deletesthe logical address of the original track group 501. Consequently, thetrack group 501 is set as a new spare track group.

In the process illustrated in FIG. 6, the writing control is performedon the spare track group 601 only, and any data in the original trackgroup 501 is not updated. Therefore, the data in the track group 501 isalways protected, and no data is lost even if the power shuts downunexpectedly. Furthermore, no recovering process is particularlyrequired even if the power shuts down during the process illustrated inFIG. 6. Assuming that a recovering process is performed, the data storedin the spare track group 601 can simply be discarded to allow thewriting module 302 to start writing data from the beginning of the sparetrack group 601.

In the magnetic disk device 1 according to the embodiment, when a writeis performed using the shingle recording technique, the escape area 401in the magnetic disk 11 is used. However, because the capacity of theescape area 401 is limited, it is necessary not to overuse the capacity.

If all of the write commands received by the input module 301 are fordata of relatively small blocks, all of the data can be stored in theescape area 401 without overusing the escape area 401. However, if theinput module 301 receives sequential write commands, which are oftenobserved in copying a large file or the like, the escape area 401 willbe overused. If the amount of data stored in the escape area 401increases, a number of the writing of the data of the tracks by theshingle recording technique increases. Accordingly, the performance willdeteriorate significantly.

Hence, in the magnetic disk device 1 according to the embodiment, whenthe input module 301 receives sequential write commands, the writingmodule 302 begins to write data for the write commands to the escapearea 401. Then, at the timing when a logical address specified as atarget address for the sequential writes changes from the address of thefirst track group for writing data to the address of the next trackgroup, the writing module 302 starts writing the subsequent datadirectly to the spare track group thereafter. When the writing module302 completes writing data to the spare track group, the writing module302 assigns a logical address to the spare track group, and sets thetrack group originally being updated as new spare track group. If thewrite commands still continue, the writing module 302 further continueswriting data to the spare track group that is newly made available.Sequential write commands can be handled by repeating this process.

During the idle time and after completing writing data for thesequential write commands according to the process explained above, themagnetic disk device 1 merges the data written to the escape area 401and the data stored in the track groups originally being updated. Themerging process is the same as the process illustrated in FIG. 6. Inthis manner, even if the sequential write commands are received, thecapacity of the escape area 401 can be prevented from being overused byallowing data to be written directly to the spare track group during theprocess.

Furthermore, the magnetic disk device 1 explained in the firstembodiment can support a multi-threaded write. In other words, becausethe magnetic disk 11 has a spare track group for each of theheads/zones, by allowing a multi-threaded write to use the respectivespare tracks for the different heads/zones, the writing module 302 canwrite data to a plurality of track groups simultaneously.

Even if the targets of the multi-threaded write commands are in the sameheads/zones, such command can be handled by providing spare track groupsat positions that maximize the track capacity in the magnetic disk 11and making such spare track groups available for any heads/zones.

The writing in response to the write command issued in the magnetic diskdevice 1 according to the embodiment will now be explained. FIG. 7 is aflowchart of the process performed in the magnetic disk device 1according to the embodiment.

First, the input module 301 receives a write command issued by the host40 (S701). The input module 301 then receives the data to be written,transferred from the host 40 (S702). It is assumed herein that the datahas a size storable in a track or a sector comprised in a track group,and the data does not rewrite the entire track group.

Upon receipt of the write command for data having such size, the writingmodule 302 calculates a physical location in the escape area for storingthe data (S703). The physical location in the escape area may be at anylocation, and may be calculated sequentially based on the write request.In this manner, the writing module 302 calculates the location in theescape area having no relationship with the location for writing thedata specified in the write command.

The writing module 302 then writes the data to the calculated physicallocation on the magnetic disk 11 (S704). The writing module 302 thendetermines if the write is completed (S705). If the writing module 302determines that the write is not completed (No at S705), the writingmodule 302 continues writing the data at S704.

By contrast, when the writing module 302 determines that the write iscompleted (Yes at S705), the writing module 302 assigns a logicaladdress, which is previously assigned to a target location in the trackgroups specified in the write command, to the escape area in which thedata is stored. Then, the writing module 302 deletes the logical addressof the target location to prevent such an address from being referredto, and ends the process.

A process of writing data stored in the escape area 401 to a track groupin the magnetic disk device 1 according to the embodiment will now beexplained. FIG. 8 is a flowchart of the process in the magnetic diskdevice 1 according to the embodiment. It is assumed that the processillustrated in the flowchart of FIG. 8 is performed in the idle timeduring which the input module 301 receives no read/write command. Inthis manner, the reading/writing is prevented from being delayed by theprocess illustrated in FIG. 8.

First, the reading module 303 sets a track group for reading data(S801). The track group for reading data is determined based on whetherany data in the escape area is available for being merged with the datastored in such a track group, for example.

The reading module 303 then reads the data stored in the trackscomprised in the set track group (S802). The reading module 303 thendetermines if there is any data that should be merged with the data readfrom the tracks based on the set logical address (S803).

If the reading module 303 determines that there is no data that shouldbe merged (No at S803), S806 is performed without any interveningprocess.

By contrast, if the reading module 303 determines that there is somedata that should be merged (Yes at S803), the reading module 303 readsthe data temporarily stored in the escape area so that such data can bemerged with the data read from the tracks at S802 (S804).

The merging module 304 then merges the data read at S804 and the dataread from the tracks at S802 (S805).

The writing module 302 then writes the data to the tracks in the sparetrack group (S806). The writing module 302 writes the merged data whenthere is some data that should be merged, and writes the data read atS802 when there is no data that should be merged.

The writing module 302 then determines if the write of the data iscompleted in all of the tracks comprised in the spare track group(S807). If the writing module 302 determines that the write is notcompleted (No at S807), the reading module 303 starts reading the datafrom the tracks again at S802.

By contrast, if the writing module 302 determines that the write of thedata is completed in all of the tracks comprised in the spare trackgroup (Yes at S807), the writing module 302 changes the logicaladdresses so that the track group that has been read is reallocated as anew spare track group and the spare track group to which data has beenwritten is reallocated as a regular track group that makes the dataavailable for reading, and ends the process (S808). At this time, thewriting module 302 also changes the logical address assigned to theescape area.

By the process described above, the data temporarily stored in theescape area can be comprised in the regular track groups.

In the magnetic disk device 1 according to the embodiment, the data isread and written by means of the configurations described above. In thismanner, even when data is recorded to the magnetic disk 11 using theshingle recording technique, the time required for rewriting the datacan be reduced. Furthermore, when the data is to be copied from a trackgroup to a spare track group, because only the spare track group isrewritten, a data loss can be avoided even when the power shuts downunexpectedly. As described above, the technique adopted in the magneticdisk device 1 is suitable for actual production environment.

In the magnetic disk device 1 according to the embodiment, when a writecommand, especially a write command for data in a small unit, e.g.,sectors, is received, the data is once written to the escape area 401,then written to the track groups as described above. Therefore, in themagnetic disk device 1, the write can be completed in a shorter timethan the time required for writing data in the entire track group. Thus,the number of tracks comprised in a track group can be increasedcompared with a conventional example.

In the magnetic disk device 1 according to the embodiment, when data iswritten using the shingle recording technique, the spare track group isused. The data in a track group and the data in the escape area aremerged, and the merged data is written to the spare track group. In thismanner, the data is protected against a loss caused by the data beingoverwritten, and against an unexpected power shutdown.

In the magnetic disk device 1 according to the embodiment, duringsequential writes, the data is written to the spare track group insteadof the escape area, whereby the escape area is protected against overuseand performance degradation is prevented.

Furthermore, in the magnetic disk device 1 according to the embodiment,the spare track group may be provided in plurality to allow amulti-threaded write to be handled. In addition, by providing a commonspare track group to each of the heads/zones of the magnetic disk 11,versatility can be improved.

The magnetic disk controlling program executed by the CPU 26 in themagnetic disk device 1 according to the embodiment is provided in amanner pre-installed in the flash ROM 28.

Alternatively, the magnetic disk controlling program executed by the CPU26 in the magnetic disk device 1 according to the embodiment may beprovided in a manner recorded in a computer-readable recording mediumsuch as a compact disk read-only memory (CD-ROM), a flexible disk (FD),a compact disk recordable (CD-R), and a digital versatile disk (DVD) asa file in an installable or an executable format.

Furthermore, the magnetic disk controlling program executed by the CPU26 in the magnetic disk device 1 according to the embodiment may beprovided in a manner stored in a computer connected to a network such asthe Internet to be made available for downloads via the network. Themagnetic disk controlling program executed by the CPU 26 in the magneticdisk device 1 according to the embodiment may also be provided ordistributed over a network such as the Internet.

The magnetic disk controlling program executed by the CPU 26 in themagnetic disk device 1 according to the embodiment has a modularstructure comprising each of the modules explained above (the inputmodule, the writing module, the reading module, and the merging module).As the actual hardware, the CPU 26 reads the magnetic disk controllingprogram from the flash ROM 28 and executes the same. Accordingly, eachof the modules is loaded to the main memory, and the input module, thewriting module, the reading module, and the merging module are providedon the main memory.

In other words, the various modules of the systems described herein canbe implemented as software applications, hardware and/or softwaremodules, or components on one or more computers, such as servers. Whilethe various modules are illustrated separately, they may share some orall of the same underlying logic or code.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A recording medium controller configured to use a recording techniqueof collectively rewriting all tracks included in a track group, whichcomprises a plurality of tracks and is a unit for writing data, bycausing adjacent tracks to be partially overlapped with each other,comprising: a recording medium comprising a write area having theplurality of the track groups and an escape area temporarily storingdata therein; an input module configured to receive an update commandfor data recorded in the write area; a reading module configured to readdata from a first track group, which includes the data to be updated bythe update command, of the track groups; and a writing module configuredto write the data to be updated by the update command to the escape areaafter receiving the update command, and to rewrite merged data obtainedby merging the data read from the escape area and the data read from thefirst track group to each track comprised in a second track group of thetrack groups by using the recording technique.
 2. The recording mediumcontroller of claim 1, wherein, if the update command is received, thewriting module is configured to rewrite the merged data to the eachtrack comprised in the second track group during an idle time excludinga time during which a process in response to a read command or a writecommand is performed.
 3. The recording medium controller of claim 2,wherein the input module is configured to receive an update command fordata with a size storable in a sector of a track of the tracks, and thewriting module is configured to write the data with the size to beupdated by the update command to the escape area.
 4. The recordingmedium controller of claims 2, wherein the second track group is a sparearea allocated as a spare, any logical address not being assigned to thespare area until the writing module rewrites the merged data; and thewriting module is configured to assign, after rewriting the merged datato the each track of the second track group, a logical address to thesecond track group, to delete a logical address of the first trackgroup, and to set the first track group as a new spare area allocated asa spare.
 5. The recording medium controller of claim 1, wherein theinput module is configured to receive an update command for data with asize storable in a sector of a track of the tracks, and the writingmodule is configured to write the data with the size to be updated bythe update command to the escape area.
 6. The recording mediumcontroller of claims 5, wherein the second track group is a spare areaallocated as a spare, any logical address not being assigned to thespare area until the writing module rewrites the merged data; and thewriting module is configured to assign, after rewriting the merged datato the each track of the second track group, a logical address to thesecond track group, to delete a logical address of the first trackgroup, and to set the first track group as a new spare area allocated asa spare.
 7. The recording medium controller of claim 1, wherein thesecond track group is a spare area allocated as a spare, any logicaladdress not being assigned to the spare area until the writing modulerewrites the merged data; and the writing module is configured toassign, after rewriting the merged data to the each track of the secondtrack group, a logical address to the second track group, to delete alogical address of the first track group, and to set the first trackgroup as a new spare area allocated as a spare.
 8. A recording mediumcontrolling method executed by a recording medium controller configuredto use a recording technique of collectively rewriting all tracksincluded in a track group, which comprises a plurality of tracks and isa unit for writing data, by causing adjacent tracks to be partiallyoverlapped with each other, wherein, the recording medium controllercomprises a recording medium comprising a write area having theplurality of the track groups and an escape area temporarily storingdata therein, and the method comprises: receiving an update command fordata recorded in the write area; reading data from a first track group,which includes the data to be updated by the update command, of thetrack groups; and writing the data to be updated by the update commandto the escape area after receiving the update command, and rewritingmerged data obtained by merging the data read from the escape area andthe data read from the first track group to each track comprised in asecond track group of the track groups by using the recording technique.9. The recording medium controlling method of claim 8, wherein, if theupdate command is received, the writing is configured to rewrite themerged data to the each track comprised in the second track group duringan idle time excluding a time during which a process in response to aread command or a write command is performed.